The present invention relates to a vehicle airbag system, and more specifically to an igniter for the inflator of the airbag system of a motor vehicle.
A regular vehicle airbag system generally comprises (1) an inflator unit (which includes an igniter, a gas generating agent, and an inflator shell), (2) an air bag, (3) a cover, (4) an electronic control unit, and (5) an impact sensor. When the vehicle receives an impact force, the impact sensor outputs a signal to the electronic control unit, causing the electronic control unit to provide ignition current to the igniter. Upon receipt of ignition current, the igniter immediately ignites the gas generating agent, causing the air bag to be inflated within 30.about.80 milli-seconds. When the air bag is inflated, the cover is broken out suddenly, and therefore the car driver is protected. The igniter of the air bag system is required to produce a pressure about within 40.about.60 Bar within 2 milli-seconds, so that the gas generating agent can be ignited to deploy the air bag instantaneously. If the igniter fails, the air bag system becomes unable to function, and the driver may be injured seriously or killed when a collision occurred. If the igniter is excessively sensitive, the air bag may be caused to deploy by an erroneous signal. Therefore, the reliability of the igniter is critical.
Various igniters for vehicle air bag systems have been disclosed. Exemplars are seen in U.S. Pat. Nos. 4,306,499; 4,358,998; 4,959,011; 5,005,486; 5,140,906.